Literatura científica selecionada sobre o tema "Anti-oxidation protection"

In this paper, resin and vapor deposition (CVD) pyrolytic carbon coating on carbon materials was designed based on the oxidation erosion and silicification corrosion mechanism. Meanwhile the phase structure, microstructure, anti-oxidation and anti-silicification corrosion mechanisms of both coatings were studied. The surface of resin pyrolytic carbon coating has a lot of defec comparing with CVD pyrolytic carbon coating. After static oxidation test at 900 °C, the resin pyrolytic carbon coating haves some antioxidant protection ability, but after 4 h of static oxidation, weight loss rate is still as high as 30%. Antioxidant effect of CVD pyrolytic carbon coating is good, 4 h oxidation weightlessness rate is about 10%. After silicification corrosion at 1600 °C, CVD pyrolytic carbon has excellent silicification protection ability.

In recent years, some natural products isolated from the fungus of the genus Ganoderma have been found to have anti-tumor, liver protection, anti-inflammatory, immune regulation, anti-oxidation, anti-viral, anti-hyperglycemic and anti-hyperlipidemic effects.

Corrosion of metals is the gradual destruction of metal under the impact of environmental factors. Chemical or electrochemical processes on the surface of the metal cause irreversible changes in the structure of the metal. To prevent this, during storage or transport, the surfaces of metal elements must be protected against environmental factors, which include: high air humidity, acid rain and variable temperature. These factors accelerate the corrosion process, which cannot be eliminated, but can be reduced by protecting metal elements with e.g. protective oils. Some metals have the ability to passivate, which is a natural protective agent that prevents corrosion. It consists in the formation of an oxide of this metal on the metal surface. Where there is no natural protection against corrosion, protective measures must be used. This paper presents the technology for the production of protective oil for temporary protection against corrosion. The innovation of this project is that the oil will form a thin, well adhering protective layer on the metal surface, which can be easily removed. It is characterised by very low viscosity and low dripping time. It is possible to achieve by using proper base oil with carefully selected anti-corrosion additives. Based on the standard PN-75/C-04154 Petroleum products. Rust protection by metal preservatives the humidity cabinet test method, corrosion tests were carried out. The paper presents the results of a humidity cabinet test for an oil mixture based on deeply refined base oil and properly selected refining additives. The test results confirmed very good anti-corrosive properties of the developed oil due to the use of a corrosion inhibitor and an oxidation inhibitor. The thickness of the protective layer formed on the metal surface was calculated based on a mathematical formula. The resulting layer forms a thin oil film, easy to remove and protecting the metal surface from corrosion.

Cu@Sn–Bi core–shell particles were synthesized and used as conductive fillers of ink applied to flexible printed circuits. This work provides new insights into the low-temperature bonding and anti-oxidation protection of Cu-based conductive pastes.

The basic structures of Crinum Asiaticum alkaloids are N-(3, 4-dioxo-benzyl)-4-O-phenylethylamine, pyrrole phenanthridine, 5,10b-ethanophenanthridine. The basic framework can form a new parent nucleus structure with significant pharmacological activity by oxidation, dehydrogenation, cyclization, O, N-methylation, acylation reaction. Crinum Asiaticum alkaloids antibacterial, antimalarial, anti-inflammatory, anti-cancer, inducing tumor cell apoptosis, the protection of the cardiovascular and other effects are reviewed.

The succulent plant Aeonium sedifolium leaves contain several compounds that are of interest for their cosmetic uses on the skin. This study measured the inhibitory effects of enzyme production and antioxidant, astringent effects and skin wrinkles using Aeonium sedifolium leaves (ASL). The total phenolics compounds (TPC) content of ASL under optimal extraction conditions was 34.49 mg/g for hot water extract (ASLW) and 61.64 mg/g for 50% ethanol extract (ASLE). The ASLW and ASLE extracts were freeze-dried, powdered, and used as solids. TPC content, 2,2-diphenyl-1-picrylhydrazy (DPPH) radical scavenging activity, and 2,2’-azinobis (3-ethylben-zothiazoline 6-sulfonate) (ABTS) radical inhibition of the ASL phenolics were tested. The DPPH radical scavenging activities of ASLW and ASLE were tested at a TPC of 100 μg/mL. ABTS radical inhibition showed antioxidant activity of 100.00% in ASLW and ASLE, and the antioxidant protection factor of ASLW and ASLE was 1.07 and 1.22, respectively. The thiobarbituric acid-reactive substance (TBARS) inhibitory activity of ASLW and ASLE was 77.00%. The elastase inhibitory activity of ASLE was 69.03%, and collagenase inhibition activity for ASLW and ASLE was 29.82% and 54.76%, respectively. The astringent effect of ASLE was 89.82% at a TPC of 200 μg/mL. Thus, we concluded that ASL has the potential as a functional cosmetic ingredient with anti-aging effects on the skin.

The separation and identification of bioactive substances that come from natural resources have aroused increasing attention. Momordica charantia (M. charantia) has a variety of bio-activities, containing anti-oxidation, immune regulation, anti-tumor, radiation protection, anti-diabetes, and liver protection. After the extraction new substances from Momordica charantia, their treatment effect on lung cancer combined with Hedyotis diffusa was determined and the related mechanism was explored as well in this study. Firstly, the CCK-8 assay was conducted and the inhibition of the new substances combined with Hedyotis diffusa. Next, the real time RT-PCR was conducted and the relative expression of the VEGF in the cancer cells was determined. In addition, the complete chloroplast genome sequence of M. charantia is followed by the phylogenetic analysis.

The separation and identification of bioactive substances that come from natural resources have aroused increasing attention. Momordica charantia (M. charantia) has a variety of bio-activities, containing anti-oxidation, immune regulation, anti-tumor, radiation protection, anti-diabetes, and liver protection. After the extraction new substances from Momordica charantia, their treatment effect on lung cancer combined with Hedyotis diffusa was determined and the related mechanism was explored as well in this study. Firstly, the CCK-8 assay was conducted and the inhibition of the new substances combined with Hedyotis diffusa. Next, the real time RT-PCR was conducted and the relative expression of the VEGF in the cancer cells was determined. In addition, the complete chloroplast genome sequence of M. charantia is followed by the phylogenetic analysis.

Niobium (Nb)-based alloys have been extensively used in the aerospace field owing to their excellent high-temperature mechanical properties. However, the inferior oxidation resistance severely limits the application of Nb-based alloys in a high-temperature, oxygen-enriched environment. Related scholars have extensively studied the oxidation protection of niobium alloy and pointed out that surface coating technology is ideal for solving this problem. Based on the different preparation methods of Nb-based alloys’ surface coatings, this article summarizes the relevant research of domestic and foreign scholars in the past 30 years, including the slurry sintering method (SS), suspension plasma spraying method (SPS), and halide activated pack cementation method (HAPC), etc. The growth mechanism and micromorphology of the coatings access by different preparation methods are evaluated. In addition, the advantages and disadvantages of various coating oxidation characteristics and coating preparation approaches are summarized. Finally, the coating’s oxidation behavior and failure mechanism are summarized and analyzed, aiming to provide valuable research references in related fields.

Sericin-hydrogel formulations incorporating purple waxy corn (Zea mays L.) cob extract (PWCC) were developed as potential topical skin cosmetic products. Sericin has wound healing properties, protects against ultraviolet (UV) radiation, and exhibits anti-inflammatory, anti-oxidation, and anti-tyrosinase activities. PWCC is a rich source of anthocyanins with antioxidants, UV protective, anti-inflammatory, and collagen-enhancing activities. Six hydrogel formulations (S1–S6) were investigated for anti-melanogenesis on the B16F10 melanoma cell line and UV-protection on human keratinocytes (HaCaT) and anti-aging activities on normal human dermal fibroblasts (NHDFs). The results showed that the hydrogel formulations enhanced the anthocyanin permeation through the skin. The S4 formulation indicated the highest inhibition of tyrosinase activity and reduced the melanin pigment, increased the cell viability of the UV-induced HaCaT cells, the inhibition of collagenase and elastase, and increased the collagen type I production without cytotoxicity. Therefore, the PWCC loaded-sericin hydrogels show a high potential as a novel anti-hyperpigmentation, UV protection, and anti-aging products for topical applications.

AN ABSTRACT OF THE DISSERTATION OF TITLE: (OPTIMIZATION PROTECTION OF CARBOB-CARBON COMPOSITES DISC-BRAKES MATERIAL BY COATING WITH ANTI-OXIDANTS) Developing glass enhancer mixture solutions (Ki’s), which promote the formation of a stable glass layer, homogenous clear liquid solution, and low viscosity liquid form, are easy to apply, and penetrating. They are compatible with ceramic liquid glass based anti-oxidants for treating surfaces of carbon/carbon composites material, and significantly increase the rate of protection against oxidation. Ki’s’ are comprised of mixing chemical compositions at standard temperature and pressure conditions from group one and two such as Na, K, Ca, Mg, etc. of 5 to 25 wt. %, deionized water from 95 to 75 % by weight, and adding up to 1 % by weight of surfactants such as DF-16, DF-20, and CF-10 with specific proportions, and followed by thorough stirring to produce a homogeneous blend of mixture solution. The glass enhancers, which are aqueous mixture solutions, are applied to the surfaces of carbon/carbon (C/C) composites by dipping, brushing, spraying, or other painting application techniques, followed by annealing, or a heat-treating range of 80 to 110 ℃ for a minimum of 8 hours, and allowing cooling time of the coated C/C composites of a minimum of 12 hours to room temperature. Preferential compatibility of the glass enhancer mixture solutions (Ki's) is with liquid glass former's, anti-oxidants comprised mostly of borate and phosphate glasses. The glass enhancer solution mixtures (Ki’s) are supplemental additions to ceramics’ liquid anti-oxidants coatings used for carbon-carbon composites protection against oxidation, and it will increase the rate of protection against oxidation for low, and moderate temperature’s range from 400 to 900 ℃. The glass enhancer Ki’s mixture solutions should be used with liquid glass former's’ anti-oxidants, such as SiO₂, GeO₂, B₂O₃, and P₂O₅. A series of glass enhancer’s Ki’s, heat treatment cycle (char-cycle) ranged between 700 to 900 ℃, and application methods, were developed and tested experimentally. Two arbitrary isothermal temperatures of 650 ℃, and 871 ℃ were selected for thermal oxidation testing, and a temperature of 650 ℃ was selected, and tested against catalytic thermal oxidation. Additions of glass enhancer Ki’s improved protection of C/C composites disc-brakes against oxidation by double, and triple amount of time in hours versus the use of anti-oxidant coatings alone.

Carbon/Carbon (C/C) composite is defined as a carbon fiber reinforced carbon matrix. Since 1958 research has been carried out on the C/C composites. The main reason for the development of new C/C composites is the number of advantages it has to offer when compared with the regular materials. The areas where C/C composites are being used extensively are aerospace, military, etc. These C/C composites have better physical, mechanical, thermal properties when compared to steel. That is the reason C/C brakes made a huge impact in the aerospace industry. The main drawback associated with the C/C brakes which are used in aerospace applications is the oxidation of the composite at higher temperatures. Also other problem linked with the C/C brake is the migration of the inhibitors on to the friction surface of the brake which can eventually decrease the friction coefficient of the brake material. So, characterizing the commercially available Anti-Oxidant(A/O) system, developing a new A/O system which can not only provide better oxidation protection, but also an improved anti-oxidant migration resistance will be our main goal of this project.

Les travaux de cette thèse CIFRE, effectuée en collaboration entre l'UCCS et l'entreprise Mersen Gennevilliers, ont porté sur la compréhension de la protection anti-oxydation (PAO) du graphite, sur la résistance à l'exsudation du graphite protégé et sur l'élaboration de nouvelles formulations de protection. Le graphite étudié est utilisé dans le secteur aéronautique. La PAO est constituée d'une solution d'aluminophosphates imprégnée dans la porosité du graphite de façon à en protéger le volume complet. La protection obture en partie la porosité et limite l'accès aux sites actifs du graphite. Le procédé industriel d'imprégnation a été transposé au laboratoire, ce qui a permis de comparer le comportement de la PAO dans la porosité du graphite et en creuset. L'effet du traitement thermique, de l'humidité, du rapport P/Al et de la porosité sur les phases présentes a été investigué par RMN et DRX. Les pièces de graphite imprégnées étant sujettes à une dégradation en conditions hydrothermales, une phase résistante a été identifiée et stabilisée dans la porosité en faisant varier le rapport P/Al de la solution. De nouvelles formulations de PAO, où une partie de l'aluminium a été substitué par différents cations, ont été testées, et leurs performances comparées avec une solution d'aluminophophates seule, mais elles n'ont pas mené à une amélioration de la protection anti-oxydation
This work has been conducted in collaboration between UCCS and the company Mersen Gennevilliers. The aims were to investigate the existing anti-oxidation protection (AOP) of graphite and to elaborate new protective formulations. The graphite in this study is aeronautics applications. The AOP consists of an aluminophosphate solution impregnated into the porosity of the graphite to protect the entire volume. This protection seals the porosity and limits access to the active sites of the graphite. The industrial impregnation process was replicated in the laboratory, allowing a comparison of the behavior of AOP within the porosity and in a crucible (using XRD and NMR). The effect of the thermal treatment, humidity, the P/Al ratio, and porosity on its thermal evolution was investigated. The impregnated graphite pieces are regularly exposed to degradation under hydrothermal conditions. Therefore, a stable phase was stabilized within the porosity by varying the P/Al ratio of the solution. New formulations of AOP, in which a portion of the aluminum was substituted with different cations, were also tested and their performance compared with a solution of pure aluminophosphates. The new formulations did not lead to an improvement in anti-oxidation protection but provided insights into the behavior of the aluminophosphate solution within a crucible and the porosity

Les travaux de cette thèse ont été menés en collaboration entre l’UCCS et l’entreprise Safran Landing Systems (Safran LS) et ont porté sur l’élaboration d’une nouvelle voie de protection anti-oxydation (PAO) pour des matériaux composites carbone/carbone (C/C) commercialisés comme composants de freins d’avion. Le principe de cette PAO innovante est basé sur une barrière de diffusion amorphe silicatée dite interne car appliquée sous la surface du composite C/C, combinée à une phase aluminophosphate qui joue un rôle piège pour les catalyseurs d’oxydation. Cette PAO est formée par l’imprégnation des porosités du composite C/C par un mélange de précurseurs liquide, suivi d’un traitement thermique. Plusieurs voies d’imprégnation du composite C/C ont été explorées : (i) une imprégnation séquentielle du composite C/C avec une première couche d’aluminophosphate et une deuxième couche de phase vitreuse (ou inversement) ou (ii) une imprégnation simultanée du matériau avec un mélange combinant les précurseurs des deux phases. Dans un premier temps, une étude des évolutions chimiques (par RMN, micro-tomographie X synchrotron et DRX) et morphologiques (par MEBE-HT) à haute température de l’aluminophosphate a été effectuée. Cette étude a permis de comprendre l’origine de la perte d’efficacité de l’aluminophosphate après un flash thermique à 1200 °C. Puis, pour les deux voies d’imprégnation que nous avons développées, des tests de performance des PAO ont été menées en condition industrielle et des caractérisations (par RMN, MEBE-HT, analyses thermiques ATD, ATG, HSM) ont permis de relier ces performances à la structure chimique des PAO. Nous avons montré que certaines formulations de PAO séquentielles permettent d’améliorer les performances anti-oxydation en comparaison aux performances d’une PAO industrielle basée seulement sur de l’aluminophosphate
This work has been developed as part of a collaboration between the UCCS laboratory and the Safran Landing Systems (Safran LS) company. The aim of this work was to elaborate a new anti-oxidation protection (AOP) for carbon/carbon (C/C) composites marketed as airplane brakes components. The principle of this innovative AOP is based on a so-called internal silicate vitreous diffusion barrier because it is applied under the surface of the C/C composite, combined with an aluminophosphate phase which has a trapping role for the oxidation catalysts. This PAO is formed by impregnating the porosities of the C/C composite with a liquid mixture of precursors, followed by a heat treatment. Several ways of impregnating the C/C composite have been explored: (i) a sequential impregnation of the C/C composite with a first layer of aluminophosphate and a second layer of vitreous phase (or vice versa) or (ii) a simultaneous impregnation of the material with a mixture combining the precursors of the two phases. First, a study of the chemical (by NMR, X-ray micro-tomography synchrotron and XRD) and morphological (by MEBE-HT) evolutions at high temperature of the aluminophosphate was carried out. This study allowed to understand the origin of the loss of efficiency of the aluminophosphate based AOP after a thermal flash at 1200 °C. Then, for the two impregnation routes that we have developed, AOP performance tests were carried out in industrial conditions and characterizations (by NMR, MEBE-HT, thermal analyzes ATD, ATG, HSM) made it possible to link these performances to the chemical structure of the AOP. We have shown that some sequential AOP formulations improve anti-oxidation performance compared to the performance of an industrial AOP based only on aluminophosphate

The polyene macrolide RK-397 3, isolated from soil bacteria, has antifungal, antibacterial and anti-tumor activity. Tarek Sammakia of the University of Colorado has described (Angew. Chem. Int. Ed. 2007, 46, 1066) the highly convergent coupling of 1 with 2, leading to 3. The preparation of 1 depended on the powerful methods that have been developed for acyclic stereocontrol. Beginning with the allylic alcohol 4, Sharpless asymmetric epoxidation established the absolute configuration of 5. Following the Jung “non-aldol aldol” protocol, exposure of 5 to TMSOTf delivered the aldehyde 6 in high de. Condensation of 6 with the lithium enolate of acetone also proceeded with high de. The resulting alcohol was protected as the MOM ether, to direct the stereoselectivity of the subsequent aldol condensation with 8. Selective β-elimination followed by reduction and protecting group exchange then gave 1. The preparation of 2 took advantage of the power of Brown asymmetric allylation. Allylation of the symmetrical 11 led to the diol 12. This was desymmetrized by selective acetonide formation, to give 13. Ozonolysis, reductive work-up, and protection of the newly-formed 1,3-diol gave 14, setting the stage for oxidation and asymmetric allylation to give 15. Reductive deprotection and oxidation then delivered the acetonide 2. The tris acetonide 16 was assembled by addition of the enolate derived from 1 to the aldehyde 2, followed by reduction and protection. Kinetically-controlled metathesis with 17 established the triene 18. Phosphonate-mediated homologation to the pentaene 19 followed by hydrolysis and Yamaguchi macrolactonization then completed the synthesis of the macrolide RK-397 3.

Paclitaxel (Taxol®) 3 is widely used in the clinical treatment of a variety of cancers. Takaaki Sato and Noritaka Chida of Keio University envisioned (Org. Lett. 2015, 17, 2570, 2574) establishing the central eight-membered ring of 3 by the SmI2-mediated cyclization of 1 to 2. The starting point for the synthesis was the enantiomerically-pure enone 5, pre­pared from the carbohydrate precursor 4. Conjugate addition to 5 proceeded anti to the benzyloxy substituent to give, after trapping with formaldehyde and protection, the ketone 6. Reduction and protection followed by hydroboration led to 7, that was, after protection and deprotection, oxidized to 8. The second ring of 3 was added in the form of the alkenyl lithium derivative 9, prepared from the trisylhydrazone of the corresponding ketone. Hydroxyl-directed epoxidation of 10 proceeded with high facial selectivity, leading, after reduction and protection, to the cyclic carbonate 11. Allylic oxidation converted the alkene into the enone, while at the same time oxidizing the benzyl protecting group to the ben­zoate, to give 12. Reduction of the ketone 12 led to a mixture of diastereomers. In practice, only one of the diastereomers of 1 cyclized cleanly to 2, as illustrated, so the undesired diastereomer from the NaBH4 reduction was oxidized back to the enone for recycling. For convenience, only one of the diastereomers of 2 was carried forward. To establish the tetrasubstituted alkene of 3, the alkene of 2 was converted to the cis diol and on to the bis xanthate 13. Warming to 50°C led to the desired tet­rasubstituted alkene, sparing the oxygenation that is eventually required for 3. For convenience, to intercept 16, the intermediate in the Takahashi total synthesis, both xanthates were eliminated to give 14. Hydrogenation removed the disubsti­tuted alkene, and also deprotected the benzyl ether. Oxidation followed by Peterson alkene formation led to 15, that was carried on to the Takahashi intermediate 16 using the now-standard protocol for oxetane construction. It is a measure of the strength of the science of organic synthesis that Masahisa Nakada of Waseda University also reported (Chem. Eur. J. 2015, 21, 355) an elegant synthesis of 3 (not illustrated).

The Mediterranean diet has a lot of health benefits but especially because it lowers the incidence of cardiovascular diseases. It has been shown that food components, certain nutrients and the pattern of the diet lowers the risk of several diseases such as diabetes, certain cancers, obesity, respiratory disorders, mental health and cognitive decline, bone diseases (osteoarthritis), healthy aging and quality of life among more others. It has been concluded from studying the mechanism responsible for lowering these risks that food combinations, food nutrients, presence of non-nutritive substances, lifestyles habits and the cooking techniques all together make the Mediterranean dietary pattern into a tool that can not only prevent but can also be used as a way of treatment for these medical ailments. As part of the essential dietary fat, consumption of extra virgin olive oil is the main feature of Mediterranean diet. Olive oil is noted to have anti-bacterial characteristics, involved in improving the endothelial function in young females, and is hypothesized to have epigenetic effects interplay offering protection from cancers due to the presence of beneficial monounsaturated fats. The presence of antioxidants contributes to the inflammation protecting properties of the olive oil. Olive oil has high quantities of antioxidants and offers numerous benefits for cardiovascular health, such as protection of LDL from oxidation and lowering of the high blood pressure as well as offers protection from diabetes mellitus. The Mediterranean diet and the Olive oil consumption also have a fundamental impact in secondary prevention, such as in patients with atrial fibrillation that underwent catheter ablation.

The hexacyclic norditerpenoid alkaloids, including neofinaconitine 4, isolated from traditional Chinese and Japanese antiarrhythmics and analgesics, have long offered a challenge to organic synthesis. The late David Y. Gin of the Memorial Sloan-Kettering Cancer Center envisioned (J. Am. Chem. Soc. 2013, 135, 14313) an approach to 4 by way of the Diels–Alder coupling of 1 and 2. This project was completed under the supervision of his colleague Derek S. Tan. The cyclopropene 6 was prepared from the ester 5. Addition of 6 to the diene derived from 7 proceeded with modest regioselectivity to give, after enol ether hydrol­ysis, the ketone 8. After two-carbon extension of the ketone with 9 to the ester 10, ionization with HBr led to 11, that was carried on the diene 1. Opening of caprolactam 12 with ethylamine followed by oxidation delivered the aldehyde 13. Acid-mediated cyclization to the enamide followed by bromination gave 14. Carbomethoxylation followed by selenylation and oxidation completed the prep­aration of the dienophile 2. With the sterically-demanding Br blocking one face of the diene, Diels–Alder cycloaddition of 2 to 1 proceeded with high diastereocontrol, leading after hydrolysis of the intermediate silyl enol ether to the ketone 15. Oxidative cleavage of the more accessible alkene followed by elimination led to the ketone 16, that on exposure to acid underwent Mannich cyclization. Oxidation followed by elimination completed the preparation of 17. Reductive cyclization to 18 established the sixth and last ring of 4, but the tertiary alcohol was lacking. This was installed by selenylation followed by oxidation, presumably by way of the transient anti-Bredt enone. There are two classes of the norditerpenoid alkaloids, having 18 and 19 carbons respectively. The ester 19 could be a versatile precursor to both classes. For 4, the carbon had to be removed. Reduction and protection followed by oxidative cleavage gave 20, that was carried on to neofinaconitine 4.

The Streptomyces metabolite (-)-FR182877 3 binds to and stabilizes microtubules, showing the same potency of anticancer activity as Taxol (paclitaxel). Masahisa Nakada of Waseda University assembled (Angew. Chem. Int. Ed. 2009, 48, 2580) the hexacyclic ring system of 3 by the tandem intramolecular Diels-Alder–intramolecular hetero Diels-Alder cyclization of 1, generating seven new stereogenic centers in a single step. The construction of the pentaene substrate 1 started with the known aldehyde 4, prepared by homologation of commercial ethyl 3-methyl-4-oxocrotonate. Addition of the propionyl oxazolidine anion 5 proceeded with high diastereocontrol, to give 6. The acyl oxazolidinone was not an efficient acylating agent, so it was converted to the Weinreb amide. Protection and deprotection then delivered the allylic acetate 7. The key step in the pentaene assembly was the carefully optimized Negishi-Wipf methylation of 8, followed by Pd-mediated coupling of the alkenyl organometallic so generated with the allylic acetate, to give 9. Condensation of the derived keto phosphonate 11 with the known aldehyde 12 then delivered the enone 13. The Nakada group has worked extensively on the intramolecular Diels-Alder reaction of substrates such as 1. They have shown that protected anti diols such as 1 cyclize with substantial diastereocontrol and in the desired sense. In contrast, cyclizations of protected syn diols proceed with poor diastereocontrol. The enone 13 was therefore reduced to the anti diol and protected, leading to 14 . Oxidation of 14 at room temperature led to a complex mixture, but slow oxidation at elevated temperature delivered 2 . Although the yield of 2 was not much better than if the reactions were carried out sequentially, first the intramolecular Diels-Alder cyclization, then the intramolecular hetero Diels-Alder cyclization, with the cascade protocol pure 2 was more readily separated from the reaction matrix. With 2 in hand, there was still the challenge of assembling the seven-membered ring. Cyclization was effected with an intramolecular Heck protocol. The two diastereomers of the allylic alcohol 15 cyclized with comparable efficiency. Ir-catalyzed alkene migration then converted the allylic alcohols to a mixture of ketones, which was equilibrated to give the more stable diasteromer.

Some members of the indoxamycin family show potent antineoplastic activity. The key cyclopentene-forming step in the route to indoxamycin B 3 devised (Angew. Chem. Int. Ed. 2012, 51, 3474) by Erick M. Carreira of ETH Zürich was the Pd-catalyzed cyclization of 1 to 2. The starting material for the preparation of 1 was the symmetrical methyl benzoate 4. Dissolving metal reduction followed by alkylation of the resulting ester enolate delivered the diene 5. Reduction and protection followed by allylic oxidation converted 5 into 6, which was carried onto 8 as a mixture of geometric isomers. The dissociated potassium alkoxide of 8 underwent smooth oxy-Cope rearrangement to give an enolate that was trapped as the silyl ether 1. Pd-catalyzed oxidative cyclization then completed the synthesis of 2. With the ketone 2 in hand, two challenges remained: distinguishing the two hydroxymethyl groups and functionalizing the allylic methine to construct the third quaternary center. Both problems were solved by the V-mediated epoxidation of the diol corresponding to 2. In situ, the anti-hydroxyl opened the epoxide to give the cyclic ether. Gold-mediated rearrangement of the O-propargylated enol ether 10 delivered an allene, which was selectively reduced to the alcohol 11. A second gold-mediated cyclization then completed the synthesis of 12. Indoxamycin B had been assigned as having the butenyl sidechain as the more stable endo diastereomer, so the synthesis was initially finished that way. When that product proved to not be congruent with the natural material, it seemed likely that the butenyl sidechain was in fact exo. Selective hydration of 12 gave a mixture of all four alcohol diastereomers. The two exo diastereomers were separated and oxidized to the ketone 13. Wittig olefination gave a pair of geometric isomers that were separated. The cyclic ether of the E isomer 14 was reduced to give a keto alcohol, which was oxidized to the keto aldehyde. Horner-Wadsworth-Emmons chain extension gave 15, which was carried onto indoxamycin B 3. An alternative construction of 3 by intramolecular carbene insertion into the allyic methine of 2 can be imagined.

Reactive oxygen species (ROS) have been associated with a wide variety of human diseases and disorders. The ability of these molecules can incapacitate antioxidant activity leading to an imbalance between oxidants and anti-oxidants, with the latter being more pronounced. ROS are no strangers to immune cell relationships and function and consequently the development of autoimmune and inflammatory diseases. The collateral damage of excessive ROS (collectively called Oxidative stress) to the cells or tissue due to nucleic acid damage and oxidation of macromolecules such as proteins and lipids is linked to the manifestation, malfunction and translation to the disease state of cells. Contrary to this view, recent studies have shown that ROS have protective roles in certain autoimmune and inflammatory diseases. Despite significant advances in our understanding of inflammatory and autoimmune diseases, therapeutics for these diseases still need further development and identification of new targets for improved therapeutic effect. ROS molecules and inflammation modulators appear before disease development making them great therapeutic targets with the potential to inhibit disease manifestation.

Abstract The corrosion behavior of two stainless steels (310S and alumina-formed 310S) treated by different surface treatment methods (polishing or grinding) has been investigated after exposed to high-temperature supercritical carbon dioxide (sCO2) at 650°C / 20 MPa. The microstructure and microchemistry of materials have been analyzed and compared before and after exposure. The results show that polishing deteriorates the corrosion resistance, while grinding enhances the anti-oxidation and anti-carburization capability of materials. Thick and unprotective Fe-rich oxides are formed on the polished 310S and alumina-formed 310S, which leads to the poor carburization resistance. Much thinner oxides and shallower carburization depths can be observed on the materials treated by grinding. Continuous Cr-rich oxide is formed on the grinded 310S, while outer Cr-rich and inner Al-rich oxides are formed on the grinded alumina-formed 310S. Grinding deforms the surface region of materials. An outer ultra-fine grain layer and an inner highly deformed grain layer are located at the surface, which own fast diffusion paths and enhance the element diffusion rates (especially Cr and Al). This leads to the transition from the formation of unprotective Fe-rich oxide layers to the protective Cr-rich or Al-rich oxide layers, which not only hinders further oxidation of the matrix, but also reduces the carbon permeation. Improved oxidation and carburization resistance therefore occurs on the materials treated by grinding after exposed to high temperature sCO2 environment.

Abstract The isothermal and cyclic oxidation of freestanding Ni-20Cr-10Al-lY thick coatings has been investigated at 1200°C using TGA, SEM, XRD and XPS techniques. Coatings produced by HVOF are dense and remain crack free after thermal treatments. The protective oxide layer formed did not flake off upon cyclic oxidation as confirmed by SEM analysis. In addition, three oxidation regimes were identified after analyzing TGA data: two below 1000 °C and a third one at approximately 1200°C. The regimes below 1000°C correspond to the selective oxidation of elements on the surface and at the subsurface of the coatings whereas the third regime involves element diffusion from the bulk of the coating to the surface. The oxidation regime became asymptotic at 1200 °C as stable oxides formed. The presence of water vapor affects neither the thickness nor the orientation of oxide crystals formed on the surface as confirmed by the X-ray analysis. The XPS and X-ray results show an inter-diffusion between the coating and substrate with a slight increase in chromium concentration at the interface. Element distribution within the oxide layer was found to follow the order: Al-(oxide)Y-(oxide)/Cr-(oxide)/Ni-(oxide)/NiCrAlY from the outermost oxide layer to the bulk of the coating. These results show that HVOF dense Ni-20Cr-10Al-lY sprayed coatings can be used as anti-oxidant barriers in both isothermal and cyclic oxidation at 1200°C.

Marine fish oil is the richest source of long-chain n-3 polyunsaturated fatty acids (LCn3PUFAs), particularly rich in EPA and DHA, with many health benefits. Lutein and curcumin are two bioactive compounds that prevent age-related macular degeneration and provide anti-cancer and anti-inflammatory functions. Directly adding fish oil (FO), lutein, and curcumin to meat during processing can produce products rich in DHA/ EPA, lutein, and curcumin and help improve human health without changing consumers' dietary habits. However, FO, lutein, and curcumin are unstable under processing and storage conditions and can cause undesirable quality issues such as lipid oxidation and fishy odor to the meat products. Encapsulation is a common strategy to overcome these challenges, and essential oils (EO) extracted from spices can mask fishy odor and inhibit lipid oxidation during encapsulating, processing, and storage. Thus, the FO and EOs were co-encapsulated first, and then lutein and curcumin were incorporated into the encapsulate to provide more functions to the final products. All the encapsulated FO-EO powders were stable at room temperature during the first ten days of storage, but GO produced the best protective effect among the EOs. Adding lutein or curcumin to the garlic EO-FO co-encapsulate significantly increased the MDA content in the encapsulation powders after ten days of storage. Similar results were also observed in the rosemary EO-FO group. The increased MDA content in the lutein- or curcumin-added FO-EO encapsulates might be due to the long dissolving time of the lutein or curcumin in the FO, which allowed prolonged air contacts to the fish oil. The encapsulation efficiency (EE%) of the final products increased significantly when rosemary and garlic EOs, lutein, and curcumin were used, but pepper black EO resulted in a decrease in the EE, probably due to the differences in the polarities of the essential oils.

In recent years, magnesium (Mg) alloys have emerged as possible biodegradable implant materials; however the degradation rate of Mg occurs at a higher rate than tolerable for the human body. Plasma electrolytic oxidation (PEO) has been used in the past as a useful surface treatment technique to improve the anti-corrosion properties of Mg alloys by forming protective coatings. This present work focuses on the effect of electrolyte solution on the corrosion, microstructural, and nanomechanical behavior of PEO coatings for possible use in biodegradable implants. The experimental parameters applied during PEO process did influence the structure, thickness, and morphology of the coating. Microstructural characterization of the coating was carried out by X-ray diffraction (XRD), scanning electron microscopy (SEM) followed by image analysis and energy dispersive spectroscopy (EDX). Further, nanoindentation was employed to evaluate nanohardness and Young’s modulus of the PEO coating. The results show beneficial effects of the PEO coating to enhance the corrosion resistance of the uncoated AZ31 magnesium alloy. The XRD pattern shows that the components of the film vary based on electrolyte solution. The film composition does affect the nanomechanical behavior.

In recent years, legislative authorities in the US, Europe and Japan have steadily reduced engine exhaust emissions, i.e., carbon monoxide (CO), hydrocarbons (HC), sulphur, particulate matter (PM) and nitrogen oxides (NOx) to improve air quality. To meet these requirements engine manufacturers have had to make significant design changes and as a consequence new engine lubricant specifications from Industry bodies (ACEA, EMA, JAMA) and individual OEMs have had to be introduced to ensure adequate lubrication of these new engines. This has led to significant changes to heavy-duty diesel engine oil (HDDEO) oil formulation composition. Engine design modifications to increase fuel combustion efficiency such as increased peak cylinder pressure and increased fuel injection pressures have placed higher stress on piston rings and liners, bearings and valve train components [1], and improved oil consumption has meant longer oil residence time in the piston ring belt area. The practice of retarded fuel injection timing and exhaust gas recirculation (EGR) as measures to reduce NOx levels by reducing peak combustion temperature has had a considerable impact on lubricant performance. Retarded injection leads to higher soot levels which can cause valve train wear and piston ring liner wear and soot-induced thickening, whilst EGR leads to increased corrosive acids and wear in the combustion chamber. Currently in Europe, Euro 3 heavy-duty engines predominantly use retarded fuel injection as the primary NOx emission control strategy although there are cases where EGR is used. In the US, cooled EGR is used by most engine manufacturers to meet US 2002 emissions. HDDEO’s contain a combination of performance additives such as overbased metal detergents, dispersants, antiwear agents and antioxidants designed to provide wear protection, engine cleanliness, and control of soot contaminants and oxidation. Other additive components include selected viscosity index (VI) improvers and pour point depressants to provide necessary viscosity characteristics and shear stability, and also anti-foam agents for oil aeration control. To meet the increased demands from low emission engines, the chemical composition of the performance additives has been modified and levels increased. Current HDDEOs optimized to meet US and European specifications contain typically between 1.3 and 1.9%wt sulphated ash, 0.1–0.14%wt phosphorus and 0.3–1.1.wt sulphur. To meet the next generation emission standards, engines will require the use of exhaust after-treatment devices. In Europe, Euro 4 emission reductions for NOx and PM, scheduled for introduction in 2005, will require the use of either selective catalytic reduction, or the use of EGR in combination with a diesel particulate filter (DPF). To meet the US 2007 requirements, higher levels of EGR than currently used, in combination with DPFs, is envisaged by most engine builders. Exhaust after-treatment devices are already used extensively in some applications such as DPFs on city buses in Europe and the US. Further NOx restrictions are scheduled for Euro 5 in 2008 and USA in 2010. NOx absorber systems, although used in gasoline engines, are still under development for heavy-duty diesel engines and may be available for 2010. Some lubricant base oil and additive components from oil consumed in the combustion chamber are believed to adversely affect the performance of after-treatment devices. Ash material from metal detergents and zinc dithiophosphates (ZDTP) can build up in the channels within particulate filters causing blockage and potentially loss of engine power, leading to a need for frequent cleaning maintenance. The role of sulphur and phosphorus in additive components is less clear. Sulphur from fuel can either oxidize to sulphur dioxide and react through to sulphuric acid, which manifests itself as particulate, or can have a poisoning effect on the catalyst itself. However, the role of sulphur containing additives is yet to be established. Phosphorus from ZDTP antiwear components can lead to a phosphate layer being deposited on catalyst surfaces, which may impair efficiency. Concerns from OEMs regarding the possible effects of ash, sulphur and phosphorus has led to chemical limits being introduced in some new and upcoming engine oil specifications. The ACEA E6 sequence restricts sulphated ash to 1.0%wt max, phosphorus to 0.08%wt max and sulphur to 0.3%wt max, while the PC-10 category scheduled for 2007 will have maximum limits of 1.0%wt sulphated ash, 0.12%wt phosphorus and 0.4%wt sulphur. The resulting constraints on the use of conventional overbased metal detergent cleanliness additives and zinc dithiophosphate antiwear additives will necessitate alternative engine oil formulation technologies to be developed in order to maintain current performance levels. Indeed, performance requirements of engine oils are expected to become more demanding for the next generation engines where emissions are further restricted. If absorbers become a major route for NOx reduction, limits on sulphur and phosphorus are likely to be more restrictive. Oil formulations meeting ACEA E6 and PC-10 chemical limits have been assessed in several key critical lubricant specification tests, looking at valve train and piston ring/cylinder liner wear, corrosive wear in bearings, piston cleanliness and soot-induced viscosity control. It is demonstrated that it is possible to achieve MB 228.5 extended oil drain performance and API CI-4 wear, corrosion and piston cleanliness requirements for current US engines equipped with EGR [2], at a sulphated ash level of 1.0%wt, and phosphorus and sulphur levels, (0.05 and 0.17%wt, respectively), considerably lower than these chemical limits. This is achievable by the use of selected low sulphur detergents, optimized primary and secondary antioxidant systems and non-phosphorus containing, ashless supplementary antiwear additives blended in synthetic basestocks. Field trials in several city bus fleets have been conducted to assess engine oil performance and durability using one of these low sulphated ash, phosphorus and sulphur (SAPS) oil formulations and to examine lubricant effects on particulate filter performance. Engine oil durability testing was conducted in bus fleets in Germany and Switzerland. These trials, involving over 100 vehicles, cover a range of engine types, e.g., Daimler Chrysler and MAN Euro 1, 2 and 3 and different fuel types (low sulphur diesel, biodiesel, and compressed natural gas) in some MAN engines. The fleets are fitted with continuously regenerating particulate filters either from new or retrofitted. Oils were tested at standard and extended drain intervals (up to 60 000km). Used oil analysis for iron, copper, lead and aluminium with the low SAPS oil in these vehicles have shown low wear rates in all engine types and comparable with a higher 1.8% ash ACEA E4, E5 quality oil. Soot levels can vary considerably, but oil viscosity is maintained within viscosity grade, even at 8% soot loading. TBN depletion and TAN accumulation rates are low showing significant residual basicity reserve and control of acidic combustion and oxidation products. Buses in Stuttgart and Berlin have been used to investigate lubricant ash effects of engine oil on particulate filter durability. Exhaust back-pressure is routinely measured and DPF filters removed and cleaned when back pressure exceeds 100 mbar. Comparison of rate of back pressure build up as a function of vehicle distance shows reduced back pressure gradients for the low SAPS oil relative to the 1.8%wt ash oil in both engine types looked at. An average reduction in back pressure gradient of 40% was found in buses equipped with OM 906LA engines in Berlin and 25% with OM 457hLA engines at both locations. Examination of the ash content in DPFs has shown a 40% reduction in the quantity of ash with the low SAPS oil. This investigation shows that it is possible to meet current long oil drain requirements whilst meeting chemical limits for future lubricants and provide benefits in DPF durability.